[KAIST Discrete Math Seminar] FYI: TODAY Thu 4PM (Sang-hyun Kim, KAIST)

[Sang-il Oum]

FYI: The following talk today is related to discrete math.
 (Disclaimer: it is a joint work with me.)

***** Topology Seminar *****

DATE: Dec 23, Thursday

TIME: 4PM-5PM

PLACE: E6-1, ROOM 4415

SPEAKER: Sang-hyun Kim, KAIST and Tufts Univ.

TITLE: Hyperbolic Surface Subgroups of One-Ended Doubles of Free Groups

http://mathsci.kaist.ac.kr/ko/schedule/scView.php?idx=-356

The polygonality in free groups concerns the existence of a van Kampen
diagram on a closed surface with certain restrictions. By formulating
polygonality in terms of corresponding Whitehead graphs, we prove that
the double of a rank-two free group is one-ended if and only if it
contains a hyperbolic surface group. For the free groups of higher
ranks, we resolve the case when the amalgamating list of words have a
regular Whitehead graph; a key ingredient is Edmonds and Seymour's
characterizations of perfect matching polytopes. This is partially
joint work with Sang-il Oum and with Henry Wilton.